Tutorial by Examples: pre

Define a new visitor class by overriding some of the methods of ExpressionVisitor: class PrintingVisitor : ExpressionVisitor { protected override Expression VisitConstant(ConstantExpression node) { Console.WriteLine("Constant: {0}", node); return base.VisitConstant(...

For iterating more than two lists simultaneously within list comprehension, one may use zip() as: >>> list_1 = [1, 2, 3 , 4] >>> list_2 = ['a', 'b', 'c', 'd'] >>> list_3 = ['6', '7', '8', '9'] # Two lists >>> [(i, j) for i, j in zip(list_1, list_2)] [(1, '...

Using a regular expression, parse a record name that might be hierarchical. The expression looks for the final colon in the name. It returns what follows the colon, or the entire name if none: regexp_substr( {name} , '[^:]*$' )

Lets have a look at the native app lifecycle methods for different platforms. Android. //Xamarin.Forms.Platform.Android.FormsApplicationActivity lifecycle methods: protected override void OnCreate(Bundle savedInstanceState); protected override void OnDestroy(); protected override void OnPause()...

# from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer # python2 from http.server import BaseHTTPRequestHandler, HTTPServer # python3 class HandleRequests(BaseHTTPRequestHandler): def _set_headers(self): self.send_response(200) self.send_header('Content-type', 'text...

Using immutable locals: Uses less horizontal space but more vertical space than the "anonymous temporaries" template. Preferable over the "anonymous temporaries" template if the when expression is in a loop--in that case, regex definitions should be placed outside the loop. im...

Conditional predicate will be cleaner and safer by using the NSCompoundPredicate class which provides basic boolean operators for the given predicates. Objective-c AND - Condition NSPredicate *predicate = [NSPredicate predicateWithFormat:@"samplePredicate"]; NSPredicate *anotherPre...

The following statement if (conditionA && conditionB && conditionC) //... is exactly equivalent to bool conditions = conditionA && conditionB && conditionC; if (conditions) // ... in other words, the conditions inside the "if" statement just form an...

function myFunction(x, y, z) { } var args = [0, 1, 2]; myFunction(...args); The spread syntax allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) or multiple variables are expected. Just like the rest parameters s...

We will create a simple "Hello World!" app with Angular2 2.4.1 (@NgModule change) with a node.js (expressjs) backend. Prerequisites Node.js v4.x.x or higher npm v3.x.x or higher or yarn Then run npm install -g typescript or yarn global add typescriptto install typescript globally ...

pre-push script is called by git push after it has checked the remote status, but before anything has been pushed. If this script exits with a non-zero status nothing will be pushed. This hook is called with the following parameters: $1 -- Name of the remote to which the push is being done (Ex: ...

While using Image/Colour as an background in a CardView, You might end up with slight white paddings (If default Card colour is white) on the edges. This occurs due to the default rounded corners in the Card View. Here is how to avoid those margins in Pre-lollipop devices. We need to use an attribu...

Typically we represent an anary tree (one with potentially unlimited children per node) as a binary tree, (one with exactly two children per node). The "next" child is regarded as a sibling. Note that if a tree is binary, this representation creates extra nodes. We then iterate over the s...

An example of a parametric parameter of a type function: data List a = Nil | Cons a (List a) type family DoNotInspect x type instance DoNotInspect x = List x Here x is parametric because to determine the outcome of applying DoNotInspect to a type argument, the type function do not need to in...

$ cut -d, -f1,3 <<<"a,,b,c,d,e" a,b is rather obvious, but with space-delimited strings it might be less obvious to some $ cut -d ' ' -f1,3 <<<"a b c d e" a b cut cannot be used to parse arguments as the shell and other programs do.

Note: This only works for the built-in keyboard provided by iOS SWIFT: In order for the view of a UIViewController to increase the origin of the frame when it is presented and decrease it when it is hidden, add the following functions to your class: func keyboardWillShow(notification: NSNotificat...

This example is about changing the form depending on decisions the user did with the form previously. In my special case, I needed to disable a selectbox, if a certain checkbox wasn't set. So we have the FormBuilder, where we'll set the EventListener on the FormEvents::PRE_SUBMIT event. We're usin...

We can create Singleton class in such a way that developers are forced to used the shared instance (singleton object) instead of creating their own instances. @implementation MySingletonClass + (instancetype)sharedInstance { static MySingletonClass *_sharedInstance = nil; static dispa...

Assume that I have a file named in.txt: $ cat in.txt a b a c a d I only want to replace the a\nc with deleted, but not a\nb or a\nd. $ sed -e ':loop # create a branch/label named `loop` $!{ N # append the next line of input into the pattern space /\n$/!b...

Linked list representation is more efficient in terms of memory managerment. Code to show enqueue and deque in a Queue using Linklist in O(1) time. #include<stdio.h> #include<malloc.h> struct node{ int data; node* next; }; node* front = NULL; node* rear = NULL; vo...